The invention resides in a method for recognizing defective ignition systems of internal combustion engines with several cylinders wherein ignition misses are pin-pointed particularly on the basis of engine running smoothness in dependence on the ignition or injection timing of certain cylinders.
DE 40 02 210 A1 discloses such a method for engines which have only one spark plug per cylinder. Ignition misses are recognized with this method by monitoring the smoothness of the engine in as much as the angular speed of the crankshaft is measured. However, since the angular speed of the crankshaft is not only influenced by misses of the ignition system but also by forces which are transmitted from the road, via the wheels, to the drivetrain, other means are provided to make sure, without the use of expensive sensors, that admission of fuel to a faulty cylinder is discontinued as soon as possible, without making a wrong decision. The fuel supply should be discontinued because the catalytic converter could be destroyed by the unburned gases which would reach the catalytic converter if ignition misses would occur. Also, the combustion of the gases would be incomplete.
Another method and apparatus for monitoring the ignition system is described in DE 39 34 338 A1 and in DE 42 261 A1. In both cases, the angular speed variations of the crankshaft, that is, the smoothness of engine operation is used for determining misses since this method is still the most simple.
DE 40 09 305 A1 discloses an engine which has two spark plugs per cylinder for optimizing the combustion process. With such an engine, the methods for detecting ignition misses as described above can generally not be used. The torque changes generated by the failure of one of the spark plugs of a cylinder are too small; measuring the angular speed of the crankshaft will therefore not provide any useable error information. Measurements have shown that the torque loss upon failure of one of the spark plugs of a cylinder of a gasoline engine is only about 5%, a value which does not materially affect engine running smoothness, so that the monitoring of engine smoothness to determine ignition misses is not possible. The patent therefore proposes to provide, for each spark plug, special test arrangements so that failure of a spark plug can be determined and ignition can be switched over to the other spark plug. However, such test arrangements are quite involved and expensive.
Finally, for engines with fuel injection valves, it is known (DE 33 44 229 A1) to provide the injection valve with two magnetic systems for controlling the closing member wherein both magnetic systems are separately controlled. The closing member has coaxially disposed therein a second closing member for controlling a second injection opening so that the injection volume can be better controlled in accordance with the fuel requirements over the hole operating range of the engine.
It is the object of the present invention to provide a method for detecting fuel ignition misses of an engine which is usable with gasoline engines with two spark plugs per cylinder and also with Diesel engines with two injector nozzles per cylinder and which can be performed in a relatively inexpensive manner.